The major goal of this research is to study the control of respiration in asthmatic children and to investigate factors which may alter their ventilatory regulation. Indices of ventilatory responsiveness and drive are obtained by measuring ventilation, work of breathing, and the subatmospheric pressure developed during the initial 100 milliseconds of inspiration (P100) while the airway is occluded. These parameters are measured with and without added inspiratory resistance during restful breathing and while ventilation is stimulated by hypoxia and hypercapnia. Emphasis is placed on doing periodic studies on asthmatic children who have exhibited a decreased ventilatory response to hypoxia to assess whether hypoxic ventilatory response and drive improve with therapy and whether changes in pulmonary function correlate with any changes in ventilatory responsiveness to hypoxia. BIBLIOGRAPHIC REFERENCE: Morrill, C.G., and G.J.A. Cropp. Ventilatory response of asthmatic children to progressive isocapnic hypoxia. Am. Rev. Respiratory Disease (Abstract) 113(4): 255, 1976.